Elsewhere, Art Nouveau treats sexuality in an exploratory or celebratory fashion, particularly as a liberating aspect of nature, but - as Beardsley's drawings also show - it had its more claustrophobic side. All this was done at a time that we don't really have a name for but which the French call the "Belle Epoque". Interesting, isn't it, that the British only rediscovered the erotic and commercial potential of Art Nouveau during the alleged sexual liberation of the 1960s, when artists such as Allen Jones came to the fore?

Back then, however, we as a nation we did not particularly take to the style for architecture and major interiors, though at the decorator end of the market - the furniture and trinkets and fabrics - it became very popular. With the exception of the designer Margo MacDonald and her architect husband Charles Rennie Mackintosh in Scotland - who with their friends comprised a "Glasgow School" of very Art Nouveau tastes, right down to the men's cream suits and enormous floppy cravats - we seem to have regarded it as a decadent foreign thing.

Italy saw it that way, too. They sometimes called it "Stile Liberty", after the London department store which was a big promoter of the style, so ascribing it somewhat misleadingly to the Brits. Otherwise it was "Stile Floreale". For the Germans it was "Jugendstil" or Youth Style, for the Austrians "Secession", after the artistic breakaway movement of that name headed by Gustav Klimt and the architect Josef Maria Olbrich - who designed the Secession's building with its cupola of gilded leaves. What all these names had in common was the idea of youth, renewal, rebellion, freedom. This was the first mass-communication, international style, arising as if by morphic resonance, from a number of sources around the world and disseminated more or less instantly through publications and exhibitions.

The V&A show is curated by an enthusiast, Paul Greenhalgh. It is interesting to note that this is the first time such a large and complete examination of the phenomenon has been attempted. It tells you that Art Nouveau was not, until comparatively recently, considered to be a proper art-historical subject. True, it was driven in large part by commerce (though you cannot accuse Edvard Munch, say, of pandering to the chocolate-box tendency). True, it was to an extent a street style, cobbled together from a number of different existing aesthetic strands, from French Rococo to Morris wallpaper. It was certainly a fashion thing, though it lasted much more than a couple of seasons. Of course it was eclipsed totally by a different modernism, the one driven by Adolf Loos's 1908 manifesto "Ornament and crime". And yet, the way Art Nouveau flourished as a populist style, spreading rapidly like some beautiful virus only equally suddenly to disappear, tells us something important about the mood of people a century ago.

The last new century was not going to be just business as usual. Something different was going to happen, and as it approached, a bunch of disconnected youths, with differently radical agendas, in various key cities around the world, was able to persuade an older generation to buy into it. There is something valuable, and rather touching, in that. Because a century on, we have no new global style or concept of beauty. We have no sense of living in a belle epoque. We should be properly envious of that evanescent moment.